A pesticide inhibits the activity of a particular enzyme, which can therefore be used to assay for the presence of the pesticide in an unknown sample.
a) In the laboratory, the initial rate data shown in the table below were obtained. What type of inhibitor (competitive, uncompetitive, non-competitive) is the pesticide? Determine the values of Vmax, KM, and KI. v, M/min x 106 S, M No inhibitor 10-5 M inhibitor 3.3 x 10-4 56 37 5.0 x 10-4 71 47 6.7 x 10-4 88 61 1.65 x 10-3 129 103 2.21 x 10-3 149 125
b) After 50 ml of the same enzyme solution in part (a) is mixed with 50 ml of 8x10-4 M substrate and 25 ml of a test sample, the initial rate observed is 18 µM/min. What is the pesticide concentration in the test sample assuming no other inhibitors or substrates are present?